baseDir: not set by default, set all path in html files relative to this directory.

absoluteBaseDir: same as baseDir but forces path to be absolute from this point
(starting with a /).

cssmin: defaults to 'cssmin', tasks to execute to minify CSS files. Also
accepts an array of tasks like ['cssmin1', 'cssmin2']. In this case, it supposes
that the first task is able to produce a single file from numerous inputs. If it
does not, use 'concat' first like in: ['concat', 'taskonsinglefile', 'cssmin'].

jsmin: same as cssmin but for js minification process, defaults to 'uglify'.

Right now, by default grunt-usemin2 assume it is in dev mode. It means that
it will publish each files listed in src sections to its corresponding
destination and then replace sections in HTML files by a list of all moved files.

To activate the minification process, you need to be in release mode. To do so,
you have to pass a release argument to the task just like that :

grunt usemin2:release

Any argument value other than release is ignored thus making the task behave
as if in dev mode.

When the minification process is used, each task of the process is executed resulting
in a single file per section. This is the single file that will be included in the
HTML file where the section is referenced.